This proposal seeks to acquire a Zeiss LSM 710 Duo confocal/multiphoton fluorescence microscope for the Center for Cell and Molecular Imaging at Yale University School of Medicine. This microscope would replace the oldest of three confocal microscopes in our center, which is reaching the end of its useful lifespan. The ongoing renaissance in the use of light microscopy for cell and molecular biology and physiology has been driven in large part by the development of specific fluorescent probes of cell structure and function, coupled with confocal and multiphoton fluorescence microscope systems that extend our abilities to visualize and quantitative such probes in cells and tissues. Laser scanning confocal microscopy, because of its ability to "optically section" cells and tissues, provides a tool with the spatial resolution needed to define structure in live and fixed cells alike. The second, galvanometric scan head of the requested instrument furthermore would provide the temporal resolution needed to follow rapid dynamic processes in living cells. The combination of the two scan heads, along with a multiphoton laser, would furthermore provide the ability for uncaging or photo-activation in highly localized subcellular regions during rapid scanning. Specific projects that would take immediate advantage of this equipment include tracking of formation and spread of calcium waves across pancreatic acinar cells, synaptic changes underlying neural plasticity, molecular regulation of motility in neurons and fibroblasts, and regulation of the formation of calcium signals in the cell nucleus. By replacing a heavily used but outdated microscope, the requested instrument will assure that our investigators will continue to have adequate access to state-of-the-art imaging techniques.